1. Field of the Invention
The present invention relates to a keypad assembly, and in particular to a keypad assembly having three-dimensional patterns.
2. Description of Prior Art
With the progress and development of technology, modern consumers request electronic products such as mobile phone, personal digital assistant (PDA), ultra-micro personal computer (UMPC) to be designed in a more personalized and delicate manner. However, these electronic products can be only operated via keys so as to transmit signals from a user to the electronic products or vice versa. Moreover, the user requests the keys of the electronic product to be varied continuously. Therefore, it is an important issue for the manufacturers of keys to develop keys of more competitiveness to satisfy the request of modern people.
Japanese Patent Publication No. 2000-340059 discloses a conventional keypad assembly. As shown in FIG. 1, the keypad assembly includes a bottom layer 10a, a pattern layer 12a, a surface layer 14a and a colored light-transmitting film 17a. The front surface of the pattern layer 12a is provided with three-dimensional patterns 121a. The surface layer 14a is provided with troughs to correspond to the three-dimensional patterns 121a and the surface layer 14a is overlapped on the front surface of the pattern layer 12a. The back surface of the pattern layer 12a is printed with the colored light-transmitting film 17a. The bottom layer 10a is adhered to the underside of the light-transmitting film 17a. With the above arrangement, a keypad assembly can be achieved.
Further, Japanese Patent publication No. 2000-331554 discloses another kind of keypad assembly. The difference between this patent reference and the above-mentioned Patent Publication No. 2000-340059 lies in that troughs having three-dimensional patterns are formed in the surface layer, and the inner surface of the trough is coated with the light-transmitting colored film, so that the three-dimensional patterns can be seen in the surface layer. Although the above-mentioned keypad assembly has an effect of displaying the three-dimensional patterns, it can be only applied to a relative small keycap or single keycap because no light-guiding plate is provided. Therefore, for a keypad assembly having a large operating area, the conventional keypad assembly cannot satisfy this requirement for use. Further, Patent Publication No. 2000-340059 is only printed on the top surface of the three-dimensional patterns. Therefore, the whole shape of the three-dimensional pattern cannot be displayed sufficiently, and thus the recognition and aesthetic feeling thereof are not good.
Further, China Patent Publication No. CN2544299Y discloses another keypad assembly, which includes a surface layer, a first pattern layer, a refracting layer and a second pattern layer. The surface layer is a light-transmitting body. The first pattern layer is an opaque body that is overlapped with the surface layer. The first pattern layer is provided with first patterns formed by hollowed portions. The refracting layer is a translucent body that is located below the surface layer and the first pattern layer. The underside of the refracting layer is formed with a back surface. The second pattern layer is an opaque body that is attached to the back surface of the refracting layer. The second pattern layer is provided with second patterns formed by hollowed portions. The light emitted by light-emitting elements is projected toward the surface layer from the underside of the second pattern layer, so that the first and second patterns can be displayed on the surface layer, thereby achieving a multiple displaying effect. Although the above-mentioned keypad assembly has a multiple displaying effect, it relies on the fact that the first and second patterns are formed on the first and second pattern layer respectively. As a result, the total thickness of the key would be large and thus increasing the weight thereof. Therefore, it is not suitable for the electronic products that tend to be produced toward more and more compact. Further, the light-emitting element is formed underneath the second pattern layer, increasing the total height. As a result, the thickness of the electronic product cannot be reduced sufficiently. Moreover, the refracting layer is a translucent body, so that the recognition and aesthetic feeling of the displayed second pattern are not good.